Jaiminīya Upaniṣad Brāhmaṇa 2.1.3

2.1.3

te 'bruvan vācodgātrā dīkṣāmahā iti
te vācodgātrādīkṣanta
sa yad eva vācā vadati tad ātmana āgāyad atha ya itare kāmās tān devebhyaḥ /

They said: “Let us consecrate ourselves with speech as the udgātṛ.” They consecrated themselves with speech as the udgātṛ. Whatever one speaks with speech, that he sang for himself, but whatever other desires there were, those [he sang] for the gods.